There's a smart, funny comedy screaming to get out of "Krippendorf's Tribe." Unfortunately, it's buried under so many vulgar sex and other body-function jokes that all the world's shovels couldn't dig it out.

It's not like the film doesn't have a funny premise (it's based on a novel about a down-on-his-luck professor who practices "tabloid anthropology," with help from his children) or a talented cast (Richard Dreyfuss and star-on-the-rise Jenna Elfman, from TV's "Dharma & Greg").But the filmmakers continue to sabotage both by taking the low road whenever possible, and include some crass gags aimed strictly at lowbrow audiences.

Also, a final attempt to turn the comedy into a parable about parenting comes across as insincere, especially when some of the sexual humor really starts to push the PG-13 rating.

Dreyfuss stars as James Krippendorf, a widower who's been trying to raise his three dysfunctional children - contemptuous daughter Shelly (Natasha Lyonne), weirdo Mickey (Gregory Smith) and uncommunicative Edmund (Carl Michael Lindner). But to keep them fed, he's used most of a $100,000 research grant given to him and his late wife to study an undiscovered New Guinea tribe.

Wouldn't you know, the date of his big lecture finally arrives, and Krippendorf has nothing to talk about. In a panic, he "invents" a tribe known as the Shelmikedmu (an amalgamation of his children's names), and the audience is enthralled.

However, they also need documentation, so he's forced to enlist his children in the ruse, as well as his overzealous but devoted colleague Veronica Micelli (Elfman). And the Shelmikedmu become the hottest thing in anthropology since . . . well, take your pick.

Krippendorf's newfound success irks his fellow professor Ruth Allen (Lily Tomlin) and also sends up a red flag. So, she heads to New Guinea in search of the Shelmikedmu.

As mentioned, it is a funny idea, but it runs out of steam quickly.

To their credit, the cast members do try, especially Dreyfuss and Elfman, who brings her expected ditzy charm to her role. But talented actors Stephen Root (TV's "Newsradio"), Tom Poston, David Ogden Stiers and even Tomlin are wasted.

"Krippendorf's Tribe" is rated PG-13 for vulgar jokes and gags, some sexual and others relating to flatulence and other body functions, profanity, slapstick violence, sex (overheard) and brief partial nudity.